H27 on a Panasonic heat pump: Service valve error
Short answer
On a Panasonic heat pump, H27 means: Service valve error. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Service valve error.
Part involved: Refrigerant service (3-way) valves; high pressure sensor.
When it shows: During cooling operation, when:- [a] Indoor refrigerant pipe temperature at compressor startup - present indoor refrigerant pipe temperature < 2°C [b] Present high pressure - high pressure at compressor startup < 5kg/cm2 **Judgment only for first time cooling operation and not during pump down operation. Service-manual table judgement: Continue for 5 min (L, K, J MDC, J MXC, J AIO, H, F).
Likely causes:
- 1 3 way valves closed. 2 Faulty high pressure sensor. 3 Faulty indoor refrigerant pipe temperature sensor 4 Faulty outdoor unit PCB (main).
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: Not stated in the Panasonic documents opened; protection counters lock out after the stated number of occurrences.
Manual reset: User: 'Error Reset' in the remote-controller Quick Menu (H/J/K/L controllers) or OFF/ON; engineer must clear the underlying cause (service manuals: 'When error happens, the power has to be reset').
What you can check
- Read and note the code shown blinking on the remote controller (also stored under System Check > Error history). Per the Panasonic operating instructions the user may switch the system OFF/ON at the remote controller and use 'Error Reset' in the Quick Menu; if the code returns, leave the system and contact the installer (UK user guide lists Panasonic technical support as the fallback).
What the engineer will check
- Check refrigerant service valves are fully open (typically first cooling operation after installation); check high pressure sensor and indoor refrigerant pipe temperature sensor; check outdoor PCB.
Who to ask for: F-gas certified refrigeration / heat pump engineer (Panasonic-trained).
Certification: UK F-gas certification (Category I) for any refrigerant-circuit work; flammable-refrigerant competence for R32 (J/K) and R290 (L/M) units.
What you might notice
Sources
- Service Manual Hydromodule WH-SDC0509L3E5/L6E5 with WH-WDG05LE5/07LE5/09LE5 (Order No PAPAMY2307068CE) ↗ · PAPAMY2307068CE · page 189 (error codes table); 197 (self-diagnosis) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026